One of the major agricultural products of an herbal nature is lavender, an herbaceous shrub of the genus Lavendula, a member of the Mint family, known for its fernlike leaves and purple flowers. The dried flowers of lavender have been used for centuries as a fragrance source, particularly in sachets and potpourri, and they are further processed for fragrance essences and oils.
The uses of lavender flowers, leaves and oils includes use in medicinals, aromatherapy, cusine, perfumes, dyes, oils, toilet preparations, tinctures, distillation products (steam distillation of lavender oil), and the like. Different varieties have varying potentials. There are several types of lavender oil. The “true” lavender oil comes from Lavandula angustifolia and is the most highly prized oil. There is also spike lavender oil derived from Lavandula latifolia, and finally there is lavendin oil which comes from a L. augustifolia×L. latifolia hybrid cross.
True lavender is a native of the Mediterranean countries such as Italy, Spain and North Africa as well as Switzerland and France. The world production of this oil is estimated at about 200 metric tons/year. The lavendin oil-producing hybrid cross is also a native of the Mediterranean, but in recent years Bulgaria has become a major producer, and production is spreading to Australia and Tasmania. Lavendin oil is much cheaper and world wide production is thought to be about 1000 metric tons/year. Lavendin oils have been replacing lavender oil in recent years except for the most expensive products. Finally, spike lavender also comes from Spain and the Mediterranean but it thrives better in warmer climates than the other two species. World production is similar to lavender, about 150–200 metric tons/year,
The variety Lavandula intermedia cv. Grosso, “fat spike,” is very fragrant and is used as an oil source. Although regions of France and Italy are well known for commercial lavender growing and harvesting, lavender commercialization has become important in the United States, as many varieties grow well in zones 5–8. True lavender is a particularly important crop in the Sequim-Dungeness Valley region of Washington State's Olympic Peninsula, because its famous low rainfall, abundant sunshine, rocky, sandy soil and cool nights helps grow the heartiest, most lush lavender varieties in the US. The cool nights allow the flowers to mature slower. This causes the oils to concentrate more and increase in quality and scent.
Each lavender stem is crested with clusters of flower buds making up a flower head, also called an inflorescence. In all types of lavender, each individual flower bud is composed of two major parts: the calyx and the corolla. Both are a source of the flower's aromatic oils. The base of each calyx is attached to the flower stem. The calyx is tubular in shape and can be slightly hairy or nearly smooth (as with English lavenders) or quite rough and woolly (as with French lavender). The flower (corolla) emerges from the open end of the tubular calyx, which may, as with French lavender, end in a hoodlike shape. The corolla is slightly trumpet shaped and tubular, with five lobes. The corollas open randomly: portions of each flower head bloom, while other parts remain as hollow or seed-filled calyxes—although they start to bloom near the bottom of the flower heads.
The Spanish lavenders have showy, richly colored bracts (often called wings, rabbit ears, or flags in honor of their ornamental prominence) extending from the top of the flower head, which like all lavenders, is made up of calyxes with tiny blossoms (corollas). The less showy pale mauve bracts of French lavender protrude only slightly above the flower head, and are cupped together more like praying hands.
Typically the lavender is harvested in bloom or at the end of the blooming season. The stalks with flower heads are tied in bundles of from 30 to several hundred, then dried. Drying modes include air drying, oven drying, microwave drying, and freeze-drying. The most common process involves hanging bundles to dry in an inverted position in curing sheds or other facilities. The drying period ranges from several weeks to months, depending on the variety and the use, and the specific drying regimen, including heat and humidity.
Then the dried bundles of lavender are processed to remove the dried flower buds (corollas/calyxes) wherein the fragrance-containing essential oils are concentrated. The process has not changed in centuries: The dried inflorescences or spikes of buds are cut or snapped off the stems, and residual bracts, leaves and petals are shaken out, with the buds being collected. However, large quantities of particulates are produced in this process of separation, particularly as lavender flower heads comprise tight clusters of buds. These small buds and fine particulates include natural ambient dust particles that collected on the flowers during the growing season, and organic particulates created by the crushing of friable dried flower and stem parts.
The organic dust particles are a hazard to workers employed in the separation processing. They must wear masks, and many workers find that they are, to varying degrees, allergic to the particulates. The heavy dust load created in the processing results in worker discomfort ranging from sneezing, to eye irritation, to severe asthma-like reactions.
Further, this processing is labor intensive, repetitive and slow. In addition, it is not appealing to many workers, and training is problematic, as it takes a deft touch to properly handle the dried stems and flower heads without significant loss in yield.
Accordingly, there is a need in the art for a method and mechanical apparatus for processing of dried lavender that replicates the gentle handling of experienced workers, yet is faster and reduces the environmental dust hazards.